Phenomenal Coherence of Moving Visual Patterns

Edward H. Adelson and J. Anthony Movshon

Published in
Nature, vol. 300, pp. 532-525 (1982).
When a moving grating is viewed through an aperture, only motion orthogonal to its bars is visible, as motion
parallel to the bars causes no change in the stimulus. Because there is a family of physical motions of various
directions and speeds that appear identical, the motion of the grating is ambiguous. In contrast, when two crossed
moving gratings are superimposed, the resulting plaid pattern usually moves unambiguously and predictably. In certain
cases, however, two gratings do not combine into a single coherent percept, but appear to slide across one another.
We have studied the conditions under which coherence does and does not occur, and we report here that it depends on
the relative contrasts, spatial frequencies and directions of motion of the gratings. These effects may reveal the
previously unstudied properties of a higher order stage of motion analysis.